I. Field of the Invention
This invention relates to apparatus for controlling rotary motion, and more particularly, to a disc-type brake of the spring set electromagnetic release-type and to an improved operator assembly for setting and releasing the brake.
II. Description of the Prior Art
Disc-type brakes of the type to which this invention relates have encountered general acceptance due to their compactness, economy of construction and reliability. They have presented problems, however, in that brakes designed to provide relatively high retarding torque generally also exhibit relatively fast, generally fixed braking or setting times. Such fast or abrupt braking time is undesirable in brakes utilized, for example, with motors driving escalators, hoists, ski lifts, or other devices which require relatively high retarding torque to fully brake the load, but wherein a more gradual braking or setting time is preferred for safety or other reasons.
Various prior art disc-type brakes have been provided which afford adjustment of setting or braking time. One example may be found in U.S. Pat. No. 3,682,279 issued Aug. 8, 1972 and assigned to the assignee of this application. The structure of that patent utilized an inclined camming surface and damped solenoid arrangement to provide a gradually increasing retarding torque or braking action. Such a damped solenoid arrangement is not a complete solution.
This invention is concerned with this general area and has among its objects to provide a disc-type brake which eliminates the above noted and other disadvantages of the prior art.
More specifically, the invention has among its objects to provide a disc-type brake which achieves a relatively high retarding torque, but which also provides a relatively more gradual application of that torque along with a more gradual normal braking or setting time. Further, the invention has among its objects to provide such a disc-type brake wherein a relatively more abrupt emergency braking is achieved when the speed of rotation of the motor or other device being braked increases over a predetermined upper or safe limit.